1. Field of the Invention
The present invention relates to an optical apparatus such as an interchangeable lens and an image-taking apparatus having a function for correcting image-shake caused by shake.
2. Description of Related Art
Conventionally as an image-shake correction function mounted in an optical apparatus such as a video camera, for example, a so-called electronic shake correction method which detects a shake of a device (a camera shake) by using a shake detector with an angular velocity sensor and an angular acceleration sensor or the like and is changed a reading area of a signal from an image-pickup device based on the shake.
As another example, a so-called optical shake correction method which detects the shake of the device by using the above mentioned shake detector and the lens is moved substantially perpendicular to an optical axis direction based on the shake to make the optical axis eccentric.
In either shake correction method, the output (amplified signal) from the shake detector removed a lower frequency component than a cutoff frequency via a highpass filter (hereinafter, referred to as “HPF”), and a shake correction amount is calculated by integrating a higher frequency component than the cutoff frequency using an integrator.
When the above mentioned electronic or optical shake correction is performed, even if the shake amount is equal, the correction amount differs according to a focal length of the image-taking optical system. For example, if the same correction amount as the amount of correction to a shake amount of 0.3 deg in a telephoto end of a ten-time zoom lens is given at a wide-angle end, the correction amount corresponds to the shake amount of 3.0 deg.
Therefore, a steady hand shake correction control can be performed by performing the correction according to the focal length to the output of the integrator based on focal length information of the lens without depending on the focal length.
In addition, if a normal shake correction control is performed when an user performs a panning (or a tilting), it is detected as a shake, so image-shake is not generated by performing the shake correction control immediately upon performing the panning. However, a discontinuous feeling is caused in the movement of the image as the image starts to move suddenly, when the panning is performed further, the shake amount has exceeded the range in which the shake correction control can be performed. In addition, the state of shake correction is maximum during the panning, and the shake correction to the hand shake during the panning cannot be performed. Therefore, a panning control is performed so as to avoid such an inconvenience.
In the panning control, for example, the cutoff frequency of HPF is changed higher in the case where the output of the integrator exceeds the range determined previously, and the shake amount that the shake correction control has started is increased (Japanese Patent Application Laid-Open No. H6-165020 and H11-183951).
FIG. 15 shows the relationship between the magnitude (magnitude size of the output of the integrator) of the shake amount and the cutoff frequency of HPF during the panning control. The line in FIG. 15 shows the appearance that the cutoff frequency of HPF is changed according to the change in the integrator output. When the integrator output exceeds a predetermined value A, the cutoff frequency is increased as the magnitude of the integrator output grows.
Thus, the shake correction control is limited during panning by changing the cutoff frequency according to the magnitude of the integrator output, and as a result, the movement of an image near an intention of the user can be obtained.
By the way, a method for changing the integration constant is used besides a method for changing the cutoff frequency of HPF as a panning control.
However, the large magnification of the lens is advanced, and the focal length of the lens exceeds 1000 mm on the telephoto end. Since the panning speed slows remarkably when such a lens near the telephoto end is used and an object of shooting exists at a very far distance, it is not possible to shift from a normal hand shake correction control to the panning control smoothly. Therefore, a normal hand shake correction control is executed during the panning, as a result, the object image shakes from side to side and the image which is unnatural or has a sense of discomfort will be taken.